Oregon and Idaho have asked the U.S. Environmental Protection Agency to approve a water quality plan for the Snake River below Idaho Power´s Brownlee, Oxbow and Hells Canyon dams. The plan includes an Oregon standard requiring water temperatures below Hells Canyon of 55.5 degrees when fall chinook salmon are laying their eggs.

Idaho Power is challenging the need for the strict standard in ongoing negotiations with Oregon officials. But earlier this month, the utility filed a petition asking an Oregon judge to review the standard as it faced a deadline for legal appeal.

“It´s a placeholder,” said John Prescott, Idaho Power vice president for power supply. “In the meantime, we´re still having discussions with Oregon to resolve that and other issues.”

The three dams produce enough electricity to power the entire Treasure Valley. They account for more than half of Idaho Power´s entire generating capacity.

If Oregon prevails, Idaho Power could be required to install a “temperature control structure” on its Brownlee Dam. The concept — which Idaho Power officials insist is still unproven — would allow the company to release water from different levels of the reservoir to regulate temperatures below the dams.

Dick Nichols, manager for the Oregon Department of Environmental Quality´s eastern region water quality section, said such a device may be necessary because temperatures of the water released from Hells Canyon are high enough to threaten the salmon.

“They need something,” he said. “Selective withdrawal is one way to do it.”

But Idaho Power doesn´t believe it is solely responsible for the high temperatures in Brownlee and its other reservoirs.

Other storage reservoirs upstream, irrigation diversions, industrial and municipal discharges and other human influences all contribute, the company says.

“We will mitigate for the problems we cause,” Prescott said.

The entire concept of selective withdrawal is untested, Prescott said.

“It´s a big experiment,” he said. “Nobody knows what ultimate problems it may cause.”

The Federal Energy Regulatory Commission is scheduled to hold hearings in November on Idaho Power´s request for a new license to operate the dams.

Environmentalists, Indian tribes, Oregon and others have asked federal energy officials to require Idaho Power to conduct studies of the feasibility of selective withdrawal to control river temperatures.

So far, the company has resisted. The costs of any of the studies and construction would be passed on to ratepayers.

“They are the ones who ultimately will carry the load,” said Dennis Lopez, an Idaho Power spokesman.

But no one yet knows whether a temperature control structure would be cost effective.

“Part of the problem we have with Idaho Power is they haven´t been willing to do cost estimates on the mitigation measures they don´t like,” said Sara Eddie, an attorney for Idaho Rivers United, a conservation group devoted to river protection.

Prescott said its scientific studies show the fall chinook are doing fine below Hells Canyon. Idaho Power already has made changes in its dam operations to stabilize flows during spawning.

Idaho is not involved in the negotiations or the legal action because its water quality rules are not as stringent.

“It´s because of the differences in the two standards,” said Kate Kelly, Idaho DEQ southwest regional administrator.